Solvent extraction is a well known method for recovery of aromatic hydrocarbons from a mixed hydrocarbon stream. Typically, such a hydrocarbon stream fed to an aromatics process will contain aromatic hydrocarbons such as benzene, toluene and xylenes. The relative amounts of each of these aromatic components found in the stream to be treated can be varied by the proper choice of the boiling range of the petroleum fraction subjected to solvent extraction. There are also processes that will convert other portions of the hydrocarbon stream to aromatics prior to being sent to the aromatics extraction process.
The extraction process consists of two basic columns. An extraction column contacts a solvent with the particular petroleum fraction containing aromatics. The solvent extracts the aromatics from the feed stream, and is then sent to a stripping column. In the stripping column the aromatics are removed from the solvent and the solvent is recycled back to the extraction column for reuse.
Typical solvents useful in this process are sulfolane or glycols. Diethylene glycol, dipropylene glycol or tetraethylene glycol have been used in the prior art. A description of a process using tetraethylene glycol can be found in the Oil and Gas Journal, Jan. 7, 1974, pages 2-5.
It has been discovered that substantial energy savings can be realized in the heat necessary to strip the aromatics from the solvent by using the present invention.